// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
// 3. Neither the name of the copyright holders nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
package org.springframework.asm;

/**
 * A position in the bytecode of a method. Labels are used for jump, goto, and switch instructions,
 * and for try catch blocks. A label designates the <i>instruction</i> that is just after. Note
 * however that there can be other elements between a label and the instruction it designates (such
 * as other labels, stack map frames, line numbers, etc.).
 *
 * @author Eric Bruneton
 */
public class Label {

	/**
	 * A flag indicating that a label is only used for debug attributes. Such a label is not the start
	 * of a basic block, the target of a jump instruction, or an exception handler. It can be safely
	 * ignored in control flow graph analysis algorithms (for optimization purposes).
	 */
	static final int FLAG_DEBUG_ONLY = 1;

	/**
	 * A flag indicating that a label is the target of a jump instruction, or the start of an
	 * exception handler.
	 */
	static final int FLAG_JUMP_TARGET = 2;

	/**
	 * A flag indicating that the bytecode offset of a label is known.
	 */
	static final int FLAG_RESOLVED = 4;

	/**
	 * A flag indicating that a label corresponds to a reachable basic block.
	 */
	static final int FLAG_REACHABLE = 8;

	/**
	 * A flag indicating that the basic block corresponding to a label ends with a subroutine call. By
	 * construction in {@link MethodWriter#visitJumpInsn}, labels with this flag set have at least two
	 * outgoing edges:
	 *
	 * <ul>
	 *   <li>the first one corresponds to the instruction that follows the jsr instruction in the
	 *       bytecode, i.e. where execution continues when it returns from the jsr call. This is a
	 *       virtual control flow edge, since execution never goes directly from the jsr to the next
	 *       instruction. Instead, it goes to the subroutine and eventually returns to the instruction
	 *       following the jsr. This virtual edge is used to compute the real outgoing edges of the
	 *       basic blocks ending with a ret instruction, in {@link #addSubroutineRetSuccessors}.
	 *   <li>the second one corresponds to the target of the jsr instruction,
	 * </ul>
	 */
	static final int FLAG_SUBROUTINE_CALLER = 16;

	/**
	 * A flag indicating that the basic block corresponding to a label is the start of a subroutine.
	 */
	static final int FLAG_SUBROUTINE_START = 32;

	/**
	 * A flag indicating that the basic block corresponding to a label is the end of a subroutine.
	 */
	static final int FLAG_SUBROUTINE_END = 64;

	/**
	 * The number of elements to add to the {@link #otherLineNumbers} array when it needs to be
	 * resized to store a new source line number.
	 */
	static final int LINE_NUMBERS_CAPACITY_INCREMENT = 4;

	/**
	 * The number of elements to add to the {@link #forwardReferences} array when it needs to be
	 * resized to store a new forward reference.
	 */
	static final int FORWARD_REFERENCES_CAPACITY_INCREMENT = 6;

	/**
	 * The bit mask to extract the type of a forward reference to this label. The extracted type is
	 * either {@link #FORWARD_REFERENCE_TYPE_SHORT} or {@link #FORWARD_REFERENCE_TYPE_WIDE}.
	 *
	 * @see #forwardReferences
	 */
	static final int FORWARD_REFERENCE_TYPE_MASK = 0xF0000000;

	/**
	 * The type of forward references stored with two bytes in the bytecode. This is the case, for
	 * instance, of a forward reference from an ifnull instruction.
	 */
	static final int FORWARD_REFERENCE_TYPE_SHORT = 0x10000000;

	/**
	 * The type of forward references stored in four bytes in the bytecode. This is the case, for
	 * instance, of a forward reference from a lookupswitch instruction.
	 */
	static final int FORWARD_REFERENCE_TYPE_WIDE = 0x20000000;

	/**
	 * The bit mask to extract the 'handle' of a forward reference to this label. The extracted handle
	 * is the bytecode offset where the forward reference value is stored (using either 2 or 4 bytes,
	 * as indicated by the {@link #FORWARD_REFERENCE_TYPE_MASK}).
	 *
	 * @see #forwardReferences
	 */
	static final int FORWARD_REFERENCE_HANDLE_MASK = 0x0FFFFFFF;

	/**
	 * A sentinel element used to indicate the end of a list of labels.
	 *
	 * @see #nextListElement
	 */
	static final Label EMPTY_LIST = new Label();

	/**
	 * A user managed state associated with this label. Warning: this field is used by the ASM tree
	 * package. In order to use it with the ASM tree package you must override the getLabelNode method
	 * in MethodNode.
	 */
	public Object info;

	/**
	 * The type and status of this label or its corresponding basic block. Must be zero or more of
	 * {@link #FLAG_DEBUG_ONLY}, {@link #FLAG_JUMP_TARGET}, {@link #FLAG_RESOLVED}, {@link
	 * #FLAG_REACHABLE}, {@link #FLAG_SUBROUTINE_CALLER}, {@link #FLAG_SUBROUTINE_START}, {@link
	 * #FLAG_SUBROUTINE_END}.
	 */
	short flags;

	/**
	 * The source line number corresponding to this label, or 0. If there are several source line
	 * numbers corresponding to this label, the first one is stored in this field, and the remaining
	 * ones are stored in {@link #otherLineNumbers}.
	 */
	private short lineNumber;

	/**
	 * The source line numbers corresponding to this label, in addition to {@link #lineNumber}, or
	 * null. The first element of this array is the number n of source line numbers it contains, which
	 * are stored between indices 1 and n (inclusive).
	 */
	private int[] otherLineNumbers;

	/**
	 * The offset of this label in the bytecode of its method, in bytes. This value is set if and only
	 * if the {@link #FLAG_RESOLVED} flag is set.
	 */
	int bytecodeOffset;

	/**
	 * The forward references to this label. The first element is the number of forward references,
	 * times 2 (this corresponds to the index of the last element actually used in this array). Then,
	 * each forward reference is described with two consecutive integers noted
	 * 'sourceInsnBytecodeOffset' and 'reference':
	 *
	 * <ul>
	 *   <li>'sourceInsnBytecodeOffset' is the bytecode offset of the instruction that contains the
	 *       forward reference,
	 *   <li>'reference' contains the type and the offset in the bytecode where the forward reference
	 *       value must be stored, which can be extracted with {@link #FORWARD_REFERENCE_TYPE_MASK}
	 *       and {@link #FORWARD_REFERENCE_HANDLE_MASK}.
	 * </ul>
	 *
	 * <p>For instance, for an ifnull instruction at bytecode offset x, 'sourceInsnBytecodeOffset' is
	 * equal to x, and 'reference' is of type {@link #FORWARD_REFERENCE_TYPE_SHORT} with value x + 1
	 * (because the ifnull instruction uses a 2 bytes bytecode offset operand stored one byte after
	 * the start of the instruction itself). For the default case of a lookupswitch instruction at
	 * bytecode offset x, 'sourceInsnBytecodeOffset' is equal to x, and 'reference' is of type {@link
	 * #FORWARD_REFERENCE_TYPE_WIDE} with value between x + 1 and x + 4 (because the lookupswitch
	 * instruction uses a 4 bytes bytecode offset operand stored one to four bytes after the start of
	 * the instruction itself).
	 */
	private int[] forwardReferences;

	// -----------------------------------------------------------------------------------------------

	// Fields for the control flow and data flow graph analysis algorithms (used to compute the
	// maximum stack size or the stack map frames). A control flow graph contains one node per "basic
	// block", and one edge per "jump" from one basic block to another. Each node (i.e., each basic
	// block) is represented with the Label object that corresponds to the first instruction of this
	// basic block. Each node also stores the list of its successors in the graph, as a linked list of
	// Edge objects.
	//
	// The control flow analysis algorithms used to compute the maximum stack size or the stack map
	// frames are similar and use two steps. The first step, during the visit of each instruction,
	// builds information about the state of the local variables and the operand stack at the end of
	// each basic block, called the "output frame", <i>relatively</i> to the frame state at the
	// beginning of the basic block, which is called the "input frame", and which is <i>unknown</i>
	// during this step. The second step, in {@link MethodWriter#computeAllFrames} and {@link
	// MethodWriter#computeMaxStackAndLocal}, is a fix point algorithm
	// that computes information about the input frame of each basic block, from the input state of
	// the first basic block (known from the method signature), and by the using the previously
	// computed relative output frames.
	//
	// The algorithm used to compute the maximum stack size only computes the relative output and
	// absolute input stack heights, while the algorithm used to compute stack map frames computes
	// relative output frames and absolute input frames.

	/**
	 * The number of elements in the input stack of the basic block corresponding to this label. This
	 * field is computed in {@link MethodWriter#computeMaxStackAndLocal}.
	 */
	short inputStackSize;

	/**
	 * The number of elements in the output stack, at the end of the basic block corresponding to this
	 * label. This field is only computed for basic blocks that end with a RET instruction.
	 */
	short outputStackSize;

	/**
	 * The maximum height reached by the output stack, relatively to the top of the input stack, in
	 * the basic block corresponding to this label. This maximum is always positive or {@literal
	 * null}.
	 */
	short outputStackMax;

	/**
	 * The id of the subroutine to which this basic block belongs, or 0. If the basic block belongs to
	 * several subroutines, this is the id of the "oldest" subroutine that contains it (with the
	 * convention that a subroutine calling another one is "older" than the callee). This field is
	 * computed in {@link MethodWriter#computeMaxStackAndLocal}, if the method contains JSR
	 * instructions.
	 */
	short subroutineId;

	/**
	 * The input and output stack map frames of the basic block corresponding to this label. This
	 * field is only used when the {@link MethodWriter#COMPUTE_ALL_FRAMES} or {@link
	 * MethodWriter#COMPUTE_INSERTED_FRAMES} option is used.
	 */
	Frame frame;

	/**
	 * The successor of this label, in the order they are visited in {@link MethodVisitor#visitLabel}.
	 * This linked list does not include labels used for debug info only. If the {@link
	 * MethodWriter#COMPUTE_ALL_FRAMES} or {@link MethodWriter#COMPUTE_INSERTED_FRAMES} option is used
	 * then it does not contain either successive labels that denote the same bytecode offset (in this
	 * case only the first label appears in this list).
	 */
	Label nextBasicBlock;

	/**
	 * The outgoing edges of the basic block corresponding to this label, in the control flow graph of
	 * its method. These edges are stored in a linked list of {@link Edge} objects, linked to each
	 * other by their {@link Edge#nextEdge} field.
	 */
	Edge outgoingEdges;

	/**
	 * The next element in the list of labels to which this label belongs, or {@literal null} if it
	 * does not belong to any list. All lists of labels must end with the {@link #EMPTY_LIST}
	 * sentinel, in order to ensure that this field is null if and only if this label does not belong
	 * to a list of labels. Note that there can be several lists of labels at the same time, but that
	 * a label can belong to at most one list at a time (unless some lists share a common tail, but
	 * this is not used in practice).
	 *
	 * <p>List of labels are used in {@link MethodWriter#computeAllFrames} and {@link
	 * MethodWriter#computeMaxStackAndLocal} to compute stack map frames and the maximum stack size,
	 * respectively, as well as in {@link #markSubroutine} and {@link #addSubroutineRetSuccessors} to
	 * compute the basic blocks belonging to subroutines and their outgoing edges. Outside of these
	 * methods, this field should be null (this property is a precondition and a postcondition of
	 * these methods).
	 */
	Label nextListElement;

	// -----------------------------------------------------------------------------------------------
	// Constructor and accessors
	// -----------------------------------------------------------------------------------------------

	/**
	 * Constructs a new label.
	 */
	public Label() {
		// Nothing to do.
	}

	/**
	 * Returns the bytecode offset corresponding to this label. This offset is computed from the start
	 * of the method's bytecode. <i>This method is intended for {@link Attribute} sub classes, and is
	 * normally not needed by class generators or adapters.</i>
	 *
	 * @return the bytecode offset corresponding to this label.
	 * @throws IllegalStateException if this label is not resolved yet.
	 */
	public int getOffset() {
		if ((flags & FLAG_RESOLVED) == 0) {
			throw new IllegalStateException("Label offset position has not been resolved yet");
		}
		return bytecodeOffset;
	}

	/**
	 * Returns the "canonical" {@link Label} instance corresponding to this label's bytecode offset,
	 * if known, otherwise the label itself. The canonical instance is the first label (in the order
	 * of their visit by {@link MethodVisitor#visitLabel}) corresponding to this bytecode offset. It
	 * cannot be known for labels which have not been visited yet.
	 *
	 * <p><i>This method should only be used when the {@link MethodWriter#COMPUTE_ALL_FRAMES} option
	 * is used.</i>
	 *
	 * @return the label itself if {@link #frame} is null, otherwise the Label's frame owner. This
	 * corresponds to the "canonical" label instance described above thanks to the way the label
	 * frame is set in {@link MethodWriter#visitLabel}.
	 */
	final Label getCanonicalInstance() {
		return frame == null ? this : frame.owner;
	}

	// -----------------------------------------------------------------------------------------------
	// Methods to manage line numbers
	// -----------------------------------------------------------------------------------------------

	/**
	 * Adds a source line number corresponding to this label.
	 *
	 * @param lineNumber a source line number (which should be strictly positive).
	 */
	final void addLineNumber(final int lineNumber) {
		if (this.lineNumber == 0) {
			this.lineNumber = (short) lineNumber;
		} else {
			if (otherLineNumbers == null) {
				otherLineNumbers = new int[LINE_NUMBERS_CAPACITY_INCREMENT];
			}
			int otherLineNumberIndex = ++otherLineNumbers[0];
			if (otherLineNumberIndex >= otherLineNumbers.length) {
				int[] newLineNumbers = new int[otherLineNumbers.length + LINE_NUMBERS_CAPACITY_INCREMENT];
				System.arraycopy(otherLineNumbers, 0, newLineNumbers, 0, otherLineNumbers.length);
				otherLineNumbers = newLineNumbers;
			}
			otherLineNumbers[otherLineNumberIndex] = lineNumber;
		}
	}

	/**
	 * Makes the given visitor visit this label and its source line numbers, if applicable.
	 *
	 * @param methodVisitor    a method visitor.
	 * @param visitLineNumbers whether to visit of the label's source line numbers, if any.
	 */
	final void accept(final MethodVisitor methodVisitor, final boolean visitLineNumbers) {
		methodVisitor.visitLabel(this);
		if (visitLineNumbers && lineNumber != 0) {
			methodVisitor.visitLineNumber(lineNumber & 0xFFFF, this);
			if (otherLineNumbers != null) {
				for (int i = 1; i <= otherLineNumbers[0]; ++i) {
					methodVisitor.visitLineNumber(otherLineNumbers[i], this);
				}
			}
		}
	}

	// -----------------------------------------------------------------------------------------------
	// Methods to compute offsets and to manage forward references
	// -----------------------------------------------------------------------------------------------

	/**
	 * Puts a reference to this label in the bytecode of a method. If the bytecode offset of the label
	 * is known, the relative bytecode offset between the label and the instruction referencing it is
	 * computed and written directly. Otherwise, a null relative offset is written and a new forward
	 * reference is declared for this label.
	 *
	 * @param code                     the bytecode of the method. This is where the reference is appended.
	 * @param sourceInsnBytecodeOffset the bytecode offset of the instruction that contains the
	 *                                 reference to be appended.
	 * @param wideReference            whether the reference must be stored in 4 bytes (instead of 2 bytes).
	 */
	final void put(
			final ByteVector code, final int sourceInsnBytecodeOffset, final boolean wideReference) {
		if ((flags & FLAG_RESOLVED) == 0) {
			if (wideReference) {
				addForwardReference(sourceInsnBytecodeOffset, FORWARD_REFERENCE_TYPE_WIDE, code.length);
				code.putInt(-1);
			} else {
				addForwardReference(sourceInsnBytecodeOffset, FORWARD_REFERENCE_TYPE_SHORT, code.length);
				code.putShort(-1);
			}
		} else {
			if (wideReference) {
				code.putInt(bytecodeOffset - sourceInsnBytecodeOffset);
			} else {
				code.putShort(bytecodeOffset - sourceInsnBytecodeOffset);
			}
		}
	}

	/**
	 * Adds a forward reference to this label. This method must be called only for a true forward
	 * reference, i.e. only if this label is not resolved yet. For backward references, the relative
	 * bytecode offset of the reference can be, and must be, computed and stored directly.
	 *
	 * @param sourceInsnBytecodeOffset the bytecode offset of the instruction that contains the
	 *                                 reference stored at referenceHandle.
	 * @param referenceType            either {@link #FORWARD_REFERENCE_TYPE_SHORT} or {@link
	 *                                 #FORWARD_REFERENCE_TYPE_WIDE}.
	 * @param referenceHandle          the offset in the bytecode where the forward reference value must be
	 *                                 stored.
	 */
	private void addForwardReference(
			final int sourceInsnBytecodeOffset, final int referenceType, final int referenceHandle) {
		if (forwardReferences == null) {
			forwardReferences = new int[FORWARD_REFERENCES_CAPACITY_INCREMENT];
		}
		int lastElementIndex = forwardReferences[0];
		if (lastElementIndex + 2 >= forwardReferences.length) {
			int[] newValues = new int[forwardReferences.length + FORWARD_REFERENCES_CAPACITY_INCREMENT];
			System.arraycopy(forwardReferences, 0, newValues, 0, forwardReferences.length);
			forwardReferences = newValues;
		}
		forwardReferences[++lastElementIndex] = sourceInsnBytecodeOffset;
		forwardReferences[++lastElementIndex] = referenceType | referenceHandle;
		forwardReferences[0] = lastElementIndex;
	}

	/**
	 * Sets the bytecode offset of this label to the given value and resolves the forward references
	 * to this label, if any. This method must be called when this label is added to the bytecode of
	 * the method, i.e. when its bytecode offset becomes known. This method fills in the blanks that
	 * where left in the bytecode by each forward reference previously added to this label.
	 *
	 * @param code           the bytecode of the method.
	 * @param bytecodeOffset the bytecode offset of this label.
	 * @return {@literal true} if a blank that was left for this label was too small to store the
	 * offset. In such a case the corresponding jump instruction is replaced with an equivalent
	 * ASM specific instruction using an unsigned two bytes offset. These ASM specific
	 * instructions are later replaced with standard bytecode instructions with wider offsets (4
	 * bytes instead of 2), in ClassReader.
	 */
	final boolean resolve(final byte[] code, final int bytecodeOffset) {
		this.flags |= FLAG_RESOLVED;
		this.bytecodeOffset = bytecodeOffset;
		if (forwardReferences == null) {
			return false;
		}
		boolean hasAsmInstructions = false;
		for (int i = forwardReferences[0]; i > 0; i -= 2) {
			final int sourceInsnBytecodeOffset = forwardReferences[i - 1];
			final int reference = forwardReferences[i];
			final int relativeOffset = bytecodeOffset - sourceInsnBytecodeOffset;
			int handle = reference & FORWARD_REFERENCE_HANDLE_MASK;
			if ((reference & FORWARD_REFERENCE_TYPE_MASK) == FORWARD_REFERENCE_TYPE_SHORT) {
				if (relativeOffset < Short.MIN_VALUE || relativeOffset > Short.MAX_VALUE) {
					// Change the opcode of the jump instruction, in order to be able to find it later in
					// ClassReader. These ASM specific opcodes are similar to jump instruction opcodes, except
					// that the 2 bytes offset is unsigned (and can therefore represent values from 0 to
					// 65535, which is sufficient since the size of a method is limited to 65535 bytes).
					int opcode = code[sourceInsnBytecodeOffset] & 0xFF;
					if (opcode < Opcodes.IFNULL) {
						// Change IFEQ ... JSR to ASM_IFEQ ... ASM_JSR.
						code[sourceInsnBytecodeOffset] = (byte) (opcode + Constants.ASM_OPCODE_DELTA);
					} else {
						// Change IFNULL and IFNONNULL to ASM_IFNULL and ASM_IFNONNULL.
						code[sourceInsnBytecodeOffset] = (byte) (opcode + Constants.ASM_IFNULL_OPCODE_DELTA);
					}
					hasAsmInstructions = true;
				}
				code[handle++] = (byte) (relativeOffset >>> 8);
				code[handle] = (byte) relativeOffset;
			} else {
				code[handle++] = (byte) (relativeOffset >>> 24);
				code[handle++] = (byte) (relativeOffset >>> 16);
				code[handle++] = (byte) (relativeOffset >>> 8);
				code[handle] = (byte) relativeOffset;
			}
		}
		return hasAsmInstructions;
	}

	// -----------------------------------------------------------------------------------------------
	// Methods related to subroutines
	// -----------------------------------------------------------------------------------------------

	/**
	 * Finds the basic blocks that belong to the subroutine starting with the basic block
	 * corresponding to this label, and marks these blocks as belonging to this subroutine. This
	 * method follows the control flow graph to find all the blocks that are reachable from the
	 * current basic block WITHOUT following any jsr target.
	 *
	 * <p>Note: a precondition and postcondition of this method is that all labels must have a null
	 * {@link #nextListElement}.
	 *
	 * @param subroutineId the id of the subroutine starting with the basic block corresponding to
	 *                     this label.
	 */
	final void markSubroutine(final short subroutineId) {
		// Data flow algorithm: put this basic block in a list of blocks to process (which are blocks
		// belonging to subroutine subroutineId) and, while there are blocks to process, remove one from
		// the list, mark it as belonging to the subroutine, and add its successor basic blocks in the
		// control flow graph to the list of blocks to process (if not already done).
		Label listOfBlocksToProcess = this;
		listOfBlocksToProcess.nextListElement = EMPTY_LIST;
		while (listOfBlocksToProcess != EMPTY_LIST) {
			// Remove a basic block from the list of blocks to process.
			Label basicBlock = listOfBlocksToProcess;
			listOfBlocksToProcess = listOfBlocksToProcess.nextListElement;
			basicBlock.nextListElement = null;

			// If it is not already marked as belonging to a subroutine, mark it as belonging to
			// subroutineId and add its successors to the list of blocks to process (unless already done).
			if (basicBlock.subroutineId == 0) {
				basicBlock.subroutineId = subroutineId;
				listOfBlocksToProcess = basicBlock.pushSuccessors(listOfBlocksToProcess);
			}
		}
	}

	/**
	 * Finds the basic blocks that end a subroutine starting with the basic block corresponding to
	 * this label and, for each one of them, adds an outgoing edge to the basic block following the
	 * given subroutine call. In other words, completes the control flow graph by adding the edges
	 * corresponding to the return from this subroutine, when called from the given caller basic
	 * block.
	 *
	 * <p>Note: a precondition and postcondition of this method is that all labels must have a null
	 * {@link #nextListElement}.
	 *
	 * @param subroutineCaller a basic block that ends with a jsr to the basic block corresponding to
	 *                         this label. This label is supposed to correspond to the start of a subroutine.
	 */
	final void addSubroutineRetSuccessors(final Label subroutineCaller) {
		// Data flow algorithm: put this basic block in a list blocks to process (which are blocks
		// belonging to a subroutine starting with this label) and, while there are blocks to process,
		// remove one from the list, put it in a list of blocks that have been processed, add a return
		// edge to the successor of subroutineCaller if applicable, and add its successor basic blocks
		// in the control flow graph to the list of blocks to process (if not already done).
		Label listOfProcessedBlocks = EMPTY_LIST;
		Label listOfBlocksToProcess = this;
		listOfBlocksToProcess.nextListElement = EMPTY_LIST;
		while (listOfBlocksToProcess != EMPTY_LIST) {
			// Move a basic block from the list of blocks to process to the list of processed blocks.
			Label basicBlock = listOfBlocksToProcess;
			listOfBlocksToProcess = basicBlock.nextListElement;
			basicBlock.nextListElement = listOfProcessedBlocks;
			listOfProcessedBlocks = basicBlock;

			// Add an edge from this block to the successor of the caller basic block, if this block is
			// the end of a subroutine and if this block and subroutineCaller do not belong to the same
			// subroutine.
			if ((basicBlock.flags & FLAG_SUBROUTINE_END) != 0
					&& basicBlock.subroutineId != subroutineCaller.subroutineId) {
				basicBlock.outgoingEdges =
						new Edge(
								basicBlock.outputStackSize,
								// By construction, the first outgoing edge of a basic block that ends with a jsr
								// instruction leads to the jsr continuation block, i.e. where execution continues
								// when ret is called (see {@link #FLAG_SUBROUTINE_CALLER}).
								subroutineCaller.outgoingEdges.successor,
								basicBlock.outgoingEdges);
			}
			// Add its successors to the list of blocks to process. Note that {@link #pushSuccessors} does
			// not push basic blocks which are already in a list. Here this means either in the list of
			// blocks to process, or in the list of already processed blocks. This second list is
			// important to make sure we don't reprocess an already processed block.
			listOfBlocksToProcess = basicBlock.pushSuccessors(listOfBlocksToProcess);
		}
		// Reset the {@link #nextListElement} of all the basic blocks that have been processed to null,
		// so that this method can be called again with a different subroutine or subroutine caller.
		while (listOfProcessedBlocks != EMPTY_LIST) {
			Label newListOfProcessedBlocks = listOfProcessedBlocks.nextListElement;
			listOfProcessedBlocks.nextListElement = null;
			listOfProcessedBlocks = newListOfProcessedBlocks;
		}
	}

	/**
	 * Adds the successors of this label in the method's control flow graph (except those
	 * corresponding to a jsr target, and those already in a list of labels) to the given list of
	 * blocks to process, and returns the new list.
	 *
	 * @param listOfLabelsToProcess a list of basic blocks to process, linked together with their
	 *                              {@link #nextListElement} field.
	 * @return the new list of blocks to process.
	 */
	private Label pushSuccessors(final Label listOfLabelsToProcess) {
		Label newListOfLabelsToProcess = listOfLabelsToProcess;
		Edge outgoingEdge = outgoingEdges;
		while (outgoingEdge != null) {
			// By construction, the second outgoing edge of a basic block that ends with a jsr instruction
			// leads to the jsr target (see {@link #FLAG_SUBROUTINE_CALLER}).
			boolean isJsrTarget =
					(flags & Label.FLAG_SUBROUTINE_CALLER) != 0 && outgoingEdge == outgoingEdges.nextEdge;
			if (!isJsrTarget && outgoingEdge.successor.nextListElement == null) {
				// Add this successor to the list of blocks to process, if it does not already belong to a
				// list of labels.
				outgoingEdge.successor.nextListElement = newListOfLabelsToProcess;
				newListOfLabelsToProcess = outgoingEdge.successor;
			}
			outgoingEdge = outgoingEdge.nextEdge;
		}
		return newListOfLabelsToProcess;
	}

	// -----------------------------------------------------------------------------------------------
	// Overridden Object methods
	// -----------------------------------------------------------------------------------------------

	/**
	 * Returns a string representation of this label.
	 *
	 * @return a string representation of this label.
	 */
	@Override
	public String toString() {
		return "L" + System.identityHashCode(this);
	}
}
